Replacing my lower control arms. Question.

you'll probably be ok, but anytime you mess with steering or front suspension you should have the alignment checked, just to be safe.

Depends on how much your tires mean to you. Replacing OEM control arms with OEM control arms shouldn't cause any changes in your angles. I would just keep a close eye on tire wear for the first 500 miles or so. If you notice anything even slightly out of the normal or feel anything in the steering, get it done.